We wish to determine the extent to which the reactions of bisulfite (the aqueous form of sulfur dioxide) with nucleic acids contribute to the biological damage caused by sulfur dioxide. In the coming year, we will pursue the following goals. a) to measure the extent of modification of bacterial RNA by sulfur dioxide under conditions of growth inhibition. b) the reactivity of cytosine residues in single and double-stranded DNA to deamination by bisulfite will be measured as accurately as possible. c) the products of the bisulfite-catalyzed transamination of lysine with cytidine and deoxycytidine will be characterized. Efforts will be made to demonstrate cross-linking of polylysine with polycytidylic acid and histones with DNA. d) efforts will be made to publicize the results of this research among geneticists and toxicologists, in order to promote additional tests of bisulfite mutagenesis, and to obtain better estimates of human exposure to bisulfite.